First, make the strawberry cake layers. Preheat the oven to 350° Fahrenheit and grease two 9-inch round cake pans with butter or cooking spray. First, blitz up the freeze dried strawberries in a food processor or nutribullet, then sift the powder (to remove the seeds) into a small bowl to measure out. In a medium bowl, whisk together the flour, almond flour, baking soda and powder, salt, and powdered freeze dried sifted strawberries. Then, in a large bowl, whisk together the eggs, oil, sour cream, vanilla, sugar, pureed strawberries, and milk until smooth. Add in the whisked dry ingredients and stir to combine (but don't overstir). If using, add the food coloring to your liking and stir. Pour the batter into the two greased cake pans, ensuring both pan is evenly-filled. Bake for 30-35 minutes or until a knife inserted into the center of the cakes comes out clean. Let cool and then remove from pans (let rest on a parchment-lined counter or cookie sheet) and wash to re-use pans with lemon layers.
Then, make the lemon cake layers! Use the same two 9-inch cake pans (cleaned). Grease pans with butter or cooking spray. In a medium bowl, whisk together the flour, almond flour, baking soda and powder, and salt. Then, in a large bowl, whisk together the eggs, oil, sour cream, vanilla, sugar, lemon zest, juice, and extract, and milk until smooth. Add in the whisked dry ingredients and stir to combine (but don't overstir). Pour the batter into the two greased cake pans, ensuring both pan is evenly-filled. Bake for 30-35 minutes or until a knife inserted into the center of the cakes comes out clean. Let cool and then remove from pans (let rest on a parchment-lined counter or cookie sheet).
While cake layers are cooling, make the buttercream. Start with the strawberry buttercream. In a large bowl, using an electric mixer, beat together the room temp butter, vanilla, and one cup of the powdered sugar until smooth. Add in 1 cup of the powdered sugar at a time until thicker and smooth. Add in the powdered sifted freeze dried strawberries and pureed strawberries and blend until smooth, then set aside.
Make the lemon buttercream. In another large bowl, using an electric mixer, beat together the room temp butter and one cup of the powdered sugar until smooth. Add in 1 cup of the powdered sugar at a time until thicker and smooth. Add in the lemon zest, juice, and extract and beat until smooth. Add in just one or two drops of yellow food coloring if using (I like a very light icy yellow so less color is more). Then set aside.
Before constructing, slice off the round tops of each cake layer if they aren't totally flat. Then place one lemon layer on a plate or cake stand. Add about 3/4 cup of the lemon buttercream and spread using a butterknife or frosting knife. Spread to the edges, then place one of the strawberry cakes on top. Frost this layer with strawberry buttercream, then place the second lemon layer on top and frost with more lemon buttercream. Add last strawberry layer and frost top (carefully and smooth the frosting for presentation).
At this point, you can freeze the layered cake for one hour to stiffen it up and make it easier to frost the outside. Then frost the outside with the remaining buttercream - I use blobs of each flavor and then scrape around the side so that the two colors blend together per the photos. If you want to, put excess buttercream into two piping bags and pipe on top for presentation. Add sliced strawberries in a pattern (optional) on top, then serve! I recommend freezing the cake again for 30 minutes to an hour if you'll be transporting the cake anywhere.